NITRITE DISTRIBUTIONS AND DYNAMICS AT STATION ALOHA

We used a chemiluminescence method to measure nitrite concentrations i n the water column at the U.S. JGOFS/WOCE time-series station, ALOHA ( 22 degrees 45' N, 158 degrees W), from September 1989 to November 1993 . We present a detailed time-series of nitrite in the upper 200 m in o rder to examine the dynamics of the primary nitrite maximum. Our resul ts reveal a double-peaked structure to this Feature that is consistent with a vertical separation of the reductive and oxidative microbial p rocesses responsible for nitrite production. The possibility of using the nitrite content of this upper layer as an indicator of nitrogen ex port from the euphotic zone is explored and rejected. Midwater nitrite profiles (200-1000 m) show a supra-exponential decrease in concentrat ion with depth and reveal month-to-month variability. Nitrite concentr ations in deep waters (1000-4800 m) are in the nanomolar-subnanomolar range, and are similar to Atlantic data, arguing against significant b asin-scale differences in the deep nitrite pool. Deep profiles also sh ow measurable variability on both monthly and annual timescales. We sp eculate that this deep variability may be associated with nitrate redu ction by sinking phytoplankton cells. Copyright (C) 1996 Elsevier Scie nce Ltd